Bird Cams FAQ: Great Horned Owl Nest

September 1, 2014

Answers to Your Questions About the Great Horned Owl Nest. If you’re looking for the answer to a specific question, type control-F (command-F on a Mac) and start typing in your search terms to quickly find the answer.

Nest and Eggs

Where is this nest located?

The nest is located in the crown of a loblolly pine about 75 feet above a golf course on Skidaway Island near Savannah, Georgia. The surrounding habitat is a mixture of southern pine forest and oak (referred to as a maritime forest) on the edge of extensive salt marshes just visible on camera. The tree holding the nest is dead. It was infested with turpentine beetles and spraying came too late. The good news is that owls may continue to use a nest built in a tree that later dies, for “years and years,” according to Jim Ozier at the Georgia Department of Natural Resources. The arborists who treat this tree say it can probably stand for another four to six years. The beetles have moved on to search out another stressed loblolly pine (not a healthy tree.) The cause of stress to this tree is unknown, but unrelated to the camera installation.

Do the owls use the same nest each year

Great Horned Owls nest in a wider variety of sites than any other bird in the Americas. The owls most commonly use nests built by other species in whatever tree is available, but also use cavities in trees and snags, cliffs, deserted buildings, artificial platforms, ledges, and pipes, and will even lay eggs on the ground. Only one nest will be used per year. A pair of Bald Eagles have used this nest for the past two years and successfully raised one chick in 2012 and two eaglets in 2013. Often a tree nest deteriorates so much during a season’s use by a Great Horned Owl that few can be used again in a subsequent season. This may be the last time this nest is used, depending on how well it stands up to this year’s wear and tear, although former eagle nests tend to be sturdy and substantial.

Do they mate for life?

Great Horned Owls are monogamous and members of a pair often remain on the same territory year round. Pairs may stay together for at least five years, perhaps for life. If something happens to one of the pair, the survivor will usually find another mate.

How many eggs do Great Horned Owls lay?

When were the eggs laid?

The eggs were laid during the first week of January 2015. Great Horned Owls generally only have one brood per season. Replacement clutches are possible if the eggs are taken or destroyed during incubation. The timing of laying varies with latitude. In lower latitude states, such as Florida, incubation can begin in late November. In the Carolinas, eggs are laid from late December to early January. One egg is usually laid every two days, but there can be an interval of up to one week between laying.

How big are the eggs?

Generally the first egg is the largest and the last is smallest. Eggs in the eastern U.S. and Laborador, averaged 2.2 by 1.8 inches (5.6 by 4.7 centimeters); in California, 2.1 by 1.8 inches (5.3 by 4.5 centimeters). In Los Angeles County, California, mean mass was 1.8 ounces (51.3 grams), about 3.3 percent of the female’s body mass.

No one is sitting on the eggs or young. Won’t they get cold?

It is normal for parents to leave the eggs and nestlings exposed now and then. In most cases, they don’t stay away long enough for the eggs or young to suffer harm. Great Horned Owls have evolved over millions of years to cope with variable conditions, including harsh weather. The owls are able to incubate eggs successfully when outside temperatures are below -27.4 degrees Fahrenheit (-33 degrees Centigrade). Eggs have been recorded to withstand female absence of 20 minutes at -13 degrees Fahrenheit (-25 degrees Centigrade) when the female joined her mate in hooting at a neighboring male.

What happens if the eggs are damaged?

If only one egg is damaged, the parents generally continue to incubate the others. If something happens to the entire first clutch of eggs early in the breeding season, the owls may lay a second clutch.

Why hasn’t one of the eggs hatched even though the others have hatched?

Great Horned Owls typically lay an egg every couple days until their clutch is complete. They start incubating as soon as the first egg is laid. The eggs laid first have a head start and hatch sooner than the ones laid last. In some cases, however, an egg may not hatch because it wasn’t fertilized or because the embryo didn’t develop properly.

What is “pipping”?

“Pipping” is when the chick starts breaking through its shell using a hard projection on its bill called the egg tooth. The resulting hole is the “pip” that the chick enlarges to finish hatching. Young pip the egg and emerge without assistance from the parents.

When the chick is still in the egg how does it get air to breathe?

Oxygen gets into the egg through pores in the shell. Chicks get their first big gulp of air when they pierce the membrane layer of the egg under the shell. Once they pip, they keep their bill close to the pip and the growing crack they’re working on.

Which parent sits on the nest?

Only the female incubates the eggs. She has a featherless area on her abdomen called a “brood patch” which is designed to keep the eggs warm. This patch has lots of blood vessels just beneath the skin that transfer heat to the eggs. The male does not have a brood patch.

How big is their territory?

Estimates of territory size (defended part of home range) vary widely based on nesting density, food supply, and method of measurement. Minimum circular territory size has been recorded as just under 0.1 square miles (0.2 square kilometers). Larger circular territories have been recorded at greater than one square mile (3 square kilometers).

What happens to the bird droppings and leftovers from the prey?

Nestlings usually defecate over the side of the nest after four weeks, leaving a pungent spray of “whitewash” on shrubs and saplings in the understory. Prey is swallowed whole and can be used as nest material.

Parents and Young

How can you tell the male and the female adults apart?

As in most other raptors, females are heavier than males; sexes are otherwise similar in appearance. Only the female incubates the eggs and broods the young; the male delivers the prey. Even though the female Great Horned Owl is larger than her mate, the male has a larger voice box and a deeper voice. Pairs often call together, with audible differences in pitch.

How old are the parents?

The adult birds are not banded, so we do not have a record of their age. This species is probably the most long-lived of North American owls. The oldest Great Horned Owl on record was at least 28 years old when it was found in Ohio in 2005.

How old do Great Horned Owls have to be to start breeding?

Female Great Horned Owls are able to breed at one year old. In wild populations, more young birds are expected to acquire territories and breed when food supply is high and density of already established territories is low.

An appreciable number of adults fail to establish territories and live quietly as non-hooting/non-breeding “floaters.” At Kluane, Yukon Territory, floaters overlapped broadly with defended territories, and intrusions occurred regularly, though most often at the periphery or boundaries of defended territories, probably to avoid aggressive behavior of defenders. Floaters may be sexually mature but unable to compete successfully for territory.

How many young do Great Horned Owls have in their lifetime?

Variations in annual productivity are affected by differences in clutch size and nestling survival, but by far the largest changes in annual reproductive success appear to stem from a varying proportion of females initiating a clutch. In the temperate zone, individual females skip breeding about every third year. At northern latitudes, by contrast, females synchronize their breeding attempts relative to cyclic prey conditions; as a result, annual productivity varies from 0—1.9 in Alberta, from 0—2.2 in the Yukon, and from 1.6—2.6 in Saskatchewan. In arid or semi-arid regions, extreme variations in annual reproductive success also occur as a function of either prey cycles (e.g., black-tailed jackrabbit) or irregular precipitation.

Overall lifetime reproductive success of long-lived individuals in these different situations may or may not be similar; currently no data on this is available.

How can you tell the nestlings apart?

Won’t the babies get smothered from the female sitting on them?

The female sits on, or broods, her chicks when they are very young to help keep them warm until they can grow enough feathers of their own. The female does not sit down on the chicks hard enough to smother them. The owl chicks can breathe even when their mother is brooding them.

When will the young owls get their juvenile feathers?

Great Horned Owls hatch covered with white down. After eight days the downy plumage is replaced by immature (mesoptile) yellowish-white or grayish-buff/grayish-white plumage, with flight feathers in the wings and tail beginning to rupture sheaths. After two weeks, more than 50 percent of their juvenile plumage will have emerged. At three weeks, ear-tufts already show as small compact patches. The facial disc and white bib are well defined by 11 weeks and mottled ochraceous buff coloring is nearly complete by 21 weeks. Ear tufts are fully grown by 26 weeks.

Are you going to name the chicks?

We often receive questions about whether we name the birds featured on our cams. In some cases the birds have names, in some cases they’re referred to with letters and numbers, and in other cases they’re not given names at all. In this case, our partners at Skidaway Audubon have consulted with the Georgia Department of Natural Resources and prefer not to name the birds, in a symbolic expression of respect for them as wild animals.

Are you going to band the chicks?

Banding birds with an individually numbered ring on their leg is a common practice in ornithology to mark and study individual birds. Special permits are required to band birds for scientific study. If the owls were needed in a study, then we would consider banding them, but presently the birds are not part of a study and we do not plan to band them. In order to avoid unnecessary disturbance at the nest, banding nestlings is done only when scientifically warranted.

That chick is crying. It sounds hungry! Why haven’t the parents fed it?

Although the parents may not be available to feed a young owl right away, if you keep watching, you may have a chance to see them finally come in with food. As the young grow, they can eat and digest bigger meals, and the parents may stay away from the nest for longer periods of time. In cases of severe food shortages, it’s possible that some young may starve. The youngest and weakest may be killed by siblings during food shortages. However, the surrounding environment seems to have plenty to offer our Bird Cam family.

Which parent feeds the young?

The female parent will tear food into small pieces and feed the young, bill to bill. The male brings all the food to nest until the female is no longer brooding the chicks. The number of male visits varies with prey size; he may bring five voles during the night or a single hare or duck at dawn. The female stays with the young and hunts only when food provided by the male is insufficient. During one study, there were three instances when a single parent successfully fledged owlets after the mate had disappeared or died. At Kluane, Yukon Territory, a male raised two young after the female died when the owlets were about five weeks old.

How long until the young can see?

In general, what can I expect to see as the nestlings grow?

Day 1: The chicks are unable to raise their heads and will lie limp for the first few days after hatching. At hatching the young are covered with white down, which is initially wet but dries quickly. Legs and skin are pink. They depend on their parents to bring them food and to feed them. Young show remnants of the yolk sac and retain the egg tooth for four to six days. Eyes stay closed for 9 to 11 days. The young crawl beneath their parent, grasp weakly, swallow, and gape on the first day.

Day 3: The young will start to raise their heads.

Day 6: The young will start snapping their bills.

Day 7: Young are able to cast their first pellets.

Day 9: Eyes may start to open.

Day 14: The owlets are able to locate the parents by sound. They will respond with food calls or whimpers when the adults hoot.

Day 15: The young will start to exhibit hostile behavior when intruders approach the nest. They may hiss, sway from side to side, snap their bills, and raise their wings.

Day 19: The young will start trying to focus on objects with exaggerated head movements.

Day 21: The young start to become more and more curious and begin to grasp objects in the nest and nibble them.

Day 20-27: The owlets are able to feed themselves, with food brought to the nest, although the female parent may continue to feed them.

Day 40: The young are able to climb well, at which time they may leave the nest and clamber out along a tree branch. This stage is known as branching.

Day 45-49: The young are fully feathered and capable of flight.

At seven weeks the owls are capable of three to four short flights of diminishing distance as they tire easily.

After leaving the nest, the fledglings stick together for several weeks. They often roost together in a tree in the immediate vicinity. Adults generally roost away from the young, who react to the sight of the adults with begging calls and flights towards the adults. Adults bring their young occasional food items, even into September, and deposit them, leaving the young to dismember and swallow the prey on their own.

How old are the owls when they fledge?

How big are the nestlings?

Great Horned Owls gain weight rapidly from a mean of just over an ounce (34.7 grams) at birth to 2.2 pounds (1,000 grams) at 25 days old for females, 1.7 pounds (800 grams) at 29 days old for males. During the first 4 weeks after hatching, one study found 3 young gained an average of over an ounce (33.3 grams) per day. From 29 days to fledging, the young gained an average of just under half and ounce (12.7 grams) per day, 1.6 percent of body mass. The juveniles left the nest at approximately 75 percent of adult mass; two female young first left the nest at 44 and 45 days old, with an average weight of 2.5 pounds (1,130 grams), corresponding to 73.5 percent of adult female weight; 2 male young left the nest at 43 and 49 days old, with an average weight of 2.1 pounds (957 grams).

Won’t the chicks fall out of the nest?

Why is that big one picking on that little one?

This is a natural, well-documented behavior for nestlings of some bird species, including Great Horned Owls. In some cases, the aggression may be a way for the birds to tussle and hone their skills, such as when kittens or puppies in a litter tumble about and fight. In other cases, especially when food is scarce, aggression and siblicide may result from competition for food. Usually the older siblings are bigger and may peck the younger siblings. During food shortages, the older chicks may be the only ones to survive. Aggression toward one another usually disappears within two weeks of hatching.

Will the nestlings getting pecked be OK?

Sometimes behaviors that look alarming, such as repeated pecking, do not result in serious injury. In other cases, especially during food shortages, intense aggression may result in one sibling killing the other (siblicide). Because prey is abundant in the area, we hope that all the young in this nest will survive.

Why don’t you shut the camera off during displays of sibling aggression?

We understand that people often feel upset when they witness events in nature such as predation, fighting, injury, or death. If we observe serious injury and distress, we will redirect our web page to an interim page that provides information about what is happening and that enables people to choose whether or not they wish to continue watching. However, because this is a live camera broadcasting in real time, it is possible that viewers will see upsetting events. Viewers must decide for themselves whether they are comfortable enough with this possibility. If not, they may wish to stop visiting the cam page. The owl cam is an opportunity to get an intimate, 24/7 view of nature as it is. As in real life, nature shows us beautiful and profound moments, as well as moments that seem tragic or difficult to comprehend at times. At the Cornell Lab of Ornithology, we look to nature as our teacher. We hope that you, like us, will choose to watch, question, and learn from what you see.

If a chick dies, will the parents eat it? Will they throw it out of the nest?

If a chick falls out will someone put it back?

It would depend on the circumstances. We would need to consider factors such as whether the young owlet can be safely captured; whether it is old enough to survive on its own with its parents looking after it; and whether it is injured and can be rehabilitated.

Do the parents look after the young owlets after they leave the nest?

Fledglings remain in close company for several weeks, thereafter in loose association. They often roost together in the same tree in the immediate vicinity. Adults generally roost away from the young, who react to the sight of the adults with begging calls and flights towards the adults. Fledged owls remain with parents throughout most of the summer and may be seen begging for food into October, four to five months after leaving the nest.

Will the young owls come back to the nest next year?

Most nests are used for only one season; less commonly, a well-constructed nest in a firm tree crotch has 2—10 years of use before it disintegrates. By the onset of the next nesting season, young owls would have left their birth (natal) territory. After dispersal, most owls will be excluded from breeding by the aggressive behavior of territorial owls. These owls can remain non-territorial for several years and the proportion of such non-breeding “floaters” can reach 40 percent to 50 percent of the total population when food is scarce in boreal forests. However one juvenile female was recorded to have dispersed only just over three miles (4.5 kilometers) directly into a new territory, where she bred when only one year old.

Food

What do Great Horned Owls eat?

Great Horned Owls are generalists and opportunistic feeders and have one of the broadest diets among North American owls. They take an exceptionally wide variety of prey, ranging in size from scorpions and small rodents to larger hares and rabbits as well as large birds, including ducks, geese, and herons. Surprisingly, prey size averages smaller and dietary diversity is significantly less than for the owl’s daytime ecological counterpart the Red-tailed Hawk. Over much of the Great Horned Owl’s range, their diet consists of 90 percent mammals, 10 percent birds, and usually only a small number of amphibians, reptiles, insects, and other invertebrates.

Do they eat the bones too? Why do they eat the bones?

Owls may pull the meat off of large prey and leave the carcass, but they swallow small prey whole, bones and all. Bones are broken down in the stomach to provide important nutrients such as calcium and phosphorus. Any indigestible parts of prey such as fur and undigested bones are regurgitated as a pellet.

Do they eat leaves?

How far do they travel to find food?

Territoriality appears to limit the number of breeding pairs; individuals prevented from establishing a territory live a silent existence as “floaters.” Radio-telemetry reveals that such floaters concentrate along boundaries of established territories. Floaters nonetheless are thought to be relatively stable in home range usage, with some long-distance movements and larger home ranges than territory-holding owls. In one study, median shifts in home range center for floaters were found to be from 0.4—17.6 miles (0.6—28.3 kilometers), median 3.6 miles (5.8 kilometers), which is larger than for territorial owls of between 0.1—1.9 miles (0.2—3.1 kilometers), median 0.7 miles (1.2 kilometers).

How much do they eat?

Great Horned Owls may take small prey ranging from worms, grasshoppers, and other small invertebrates weighing less than a fraction on an ounce, to large hares, skunks, or birds weighing more than 5.5 pounds (2,500 grams) (e.g., Great Blue Heron). Mean prey size varies regionally: one ounce (28 grams) in northern California, 1.5 ounces (44.5 grams) in southwest Idaho, 1.9 ounces (55 grams) in central Washington, 3.5 ounces (98 grams) in central California, and 9.4 ounces (266 grams) in Chile.

Although there is much variation among sites, years, and seasons, the general picture of a Great Horned Owl’s diet across North America is relatively consistent; however, in Montana, Microtus voles constituted 92.6 percent of year-round prey, a remarkably higher percentage than in any other study. On average, biomass of mammals is by far the largest component; e.g. in their review of 22 studies across North America, Cromrich et al. (2002) noted that mammals constituted a minimum of 93 percent of the prey base in all studies; however many of these studies were biased towards methods such as analysis of pellets and prey remains that exaggerate the number of heavier-bodied prey items.

How do they get water?

Owls get moisture from their prey. The nestlings will get water and energy from fat. When fat from prey is metabolized, or processed to release its energy, water is produced. For every gram of fat that is metabolized, the bird gets 0.04 ounces (1.1 grams) of water as well as energy. Nestlings are not provided with water for drinking. Adult owls will drink water on occasion when they are bathing.

That bird just threw up. Is it sick?

You probably observed it regurgitating or “casting a pellet.” When a prey item is swallowed whole, indigestible parts, such as fur, bone, and tough insect parts, will form a pellet in a muscular area of the stomach called the gizzard. The pellet is later regurgitated. Most raptors will cast a pellet every day. The pellets are generally cast in the roost, possibly at dawn in response to daylight.

Anatomy and Senses

How big are the Great Horned Owls?

These are large, thick-bodied owls with two prominent feathered tufts on the head. The wings are broad and rounded. In flight, the rounded head and short bill combine to create a blunt-headed silhouette. Females are heavier than males. Females average 3.8 pounds (1,706 grams) and males 2.9 pounds (1,304 grams). Average lengths range from 18.1—24.8 in (46—63 cm) and wingspan 39.8—57.1 in (101—145 cm).

Do owls have a sense of smell?

Traditionally, scientists have assumed that most birds have a poor sense of smell because the area of a bird’s brain involved in smell is relatively small compared with the area found in mammals. However, recent research reveals that birds have a high number of active genes that are associated with smell. Scientists have also discovered that some species of birds can tell each other apart by smell. So, though we don’t have all the details, owls probably do have some ability to smell.

What’s the white film that you sometimes see over the bird’s eye?

How well can Great Horned Owls see?

Unlike those of most other birds, owl eyes look are focused directly ahead. Great Horned Owl eyes are extremely large, even for an owl, relative to size of their brain; are highly adapted for nocturnal hunting; and according to Birds of North America Online, owl eyes “include a large, almost exclusively binocular field of view, a large corneal surface, a tubular-shaped eye with anteriorly placed lens, and a predominantly rod retina” with “a single, well-defined fovea.” The bright yellow color of the iris is due to the unusual xanthopterin pigment in the iris stroma. Circumferential striated muscle is the primary pupillary constrictor, and radial myoepithelium is the primary dilator. The minimum pupil diameter is attained quickly, within 176 milliseconds after exposure to a flash of light, whereas dilation takes 1 second. In one study, a Great Horned Owl approached a dead mouse directly under very low light intensity (13 x 10—6 foot-candles), but at 28 x 10—7 foot-candles it found a mouse only by random searching. In complete blackness, the owl did not attempt to search for mice.

How well can Great Horned Owls hear?

The facial disc, which acts as a parabola to direct and concentrate sound waves toward the ears, is not as well developed as in the Great Gray Owl. Ears are bilaterally symmetrical. The large skull allows ears to be widely separated. The skull width is the only skeletal measurement that is larger in males than females. The outer ear openings have a vertical axis of 0.9 inches (23 millimeters) and hearing is acute. The ear tufts are thought to play no role in their hearing.

The facial disk is similar to a radar dish, collecting sounds and directing them to the ears. Owls can tell which direction a sound is coming from because of the minute time difference between when the sound is heard between the left and the right ear. Owls will turn their heads so the sound hits both ears simultaneously and therefore the bird is able to look in the exact direction at which the sound is coming from. The left-right sound difference is detected at 0.0003 seconds (30 millionths of a second). As the Great Horned Owl’s ears are bilaterally symmetrical they are able to line up with the sound on a vertical plane, which helps the bird create a mental image of the space where the sound is coming from. An owl’s hearing range is not unlike humans, however an owl’s hearing is more acute at certain frequencies. When hunting, the owl will fly towards the sound keeping its head in line with the location of the noise. Corrections can be made mid-flight with the prey’s movements. The brain of an owl is thought to be much more complex than that of other birds in regards to hearing.

Do owls have teeth?

Why is the poop white?

Bird poop is actually brown. The white pasty excrement is uric acid, the equivalent of a mammal’s urine. Mammals excrete waste as urea dissolved in urine; birds excrete it as uric acid, which has a low solubility in water, so it comes out as a white paste.

When it’s cold, are the birds in danger of freezing to death?

Why is the bird standing on one leg?

It is perfectly normal for an owl to stand on one leg while resting or roosting. They will sometimes alternate legs. They may do this as a heat-saving measure, keeping the raised leg warm against their stomach, or as a way to reduce fatigue in the raised leg. Birds may also shift legs just to be more comfortable, the same way humans will readjust their position!

How strong is a Great Horned Owl?

What sounds do Great Horned Owls make?

Vocalizations are varied and difficult to characterize. The number of syllables varies, even for a single individual. Male vocalizations are more elaborate, more prolonged, richer, deeper, and more mellow than those of the female.

Owlets begin to vocalize inside the egg a few hours before hatching, uttering weak whimpering cries that may serve to attract the attention of the incubating female. Shortly after hatching, the young make a single, rasping chirp, and by several days of age, faint whimpering notes. Vocalizations of the owlets in the nest rapidly increase in intensity, loudness, pitch, and character. Juvenile males mimic adult hoots during their first winter, but the calls peter out in gasps, gurgles, or squawks before completion. Females do not appear to mimic hooting, but suddenly give full female hoots in their first spring.

Although on occasion Great Horned Owls exhibit “an indescribable assemblage of hoots, chuckles, screeches, and squawks, given so rapidly and disconnectedly that the effect is both startling and amusing” (Baumgartner 1938: 274), most adults give monotonous hoots and also barks, with a variation of wac-wac when disturbed. Female vocalizations are higher in pitch because of their smaller syrinx. They will make sounds when stressed, angry, disturbed, for territorial advertisement, for mating, and as threats.

The typical territorial advertisement “song” consists of a “solemn, deep-toned hooting” with “great carrying power . . . likened . . . to the sound of a distant foghorn, a soft, somewhat tremulous, and subdued hoot, with little or no accent,” of three to six notes: who-hoo-ho-oo or who-ho-o-o, whoo-hoo-o-o, whoo (Bent 1938: 316–318). Territorial hoots are typically delivered with the beak closed, a forward leaning posture, and the tail often cocked upright.

Both sexes can utter screams though the female does it more often. It’s a high-pitched, hawk-like, piercing scream, especially pronounced during nest defense. Young also give a hawk-like scream to communicate their position to the adults, as a begging call for food, and to indicate stress or danger.

Great Horned Owls are most active vocally for less than an hour after sunset, and for a shorter period before sunrise. Sometimes an additional bout of territorial hoots or duetting can be heard around midnight or 1:00 a.m.

More Great Horned Owl facts

What predators are threats to Great Horned Owls? What other dangers do owls face?

Only when an owl nest is left unattended or an adult is driven from the nest by human activity is there predation on eggs and nestlings by crows or ravens. Owlets that tumble prematurely from the nest are susceptible to predation by red foxes and coyotes. Raccoons are known to eat eggs and nestlings, but it is not known whether opossums, wolverines, lynx, and foxes might do the same, especially at some ledge nests. Fledglings can be killed by bobcats, lynx, and coyotes, particularly when weakened by food shortage or disease.

Nestlings and fledglings are at times killed by their parents (rarely) and by older siblings (cannibalism or siblicide), especially during times of prey shortage. Great Horned Owls have also been reported attacking and killing each other. Starvation, physical injuries from other predators, and injuries from prey can also cause death within the species.

Post-fledging survival appears closely linked to the availability of food. The most likely cause of mortality among juvenile and immature owls in Kluane, Yukon Territory, was a combination of food shortages, blood-sucking flies, and a blood parasite. Although survival rates from banding studies may be biased, the best documented evidence of the effect of food supply on survival rates of Great Horned Owls is from a long-term banding effort spanning three 10-year population cycles of snowshoe hares in Saskatchewan. Annual survival rates were higher for all age classes in years when hares were abundant than in years when hares were scarce.

Adults are safe from most predators and competitors; mutual mortality has been recorded after an encounter with a black racer snake and a Red-shouldered Hawk and there has been one record of mortality from consumption of a toxic California newt.

Both the disseminated visceral form of avian tuberculosis and acute systemic herpes virus infections may be fatal in Great Horned Owls. There have been records of deaths caused by the following: septicemia with splenic abscesses, necrotizing pneumonia caused by the fungus Aspergillus niger, avian vacuolar myelinopathy, spontaneous Sarcocystis falcatula-associated encephalitis, avian mycobacteriosis, chronic myelogenous leukemia, disseminated lymphoma, and anemia and infection from the blood parasite Leucocytozoon. There have also been records of West Nile virus. A few reports of neurological abnormalities have been noted at wildlife centers.

Great Horned Owls are occasionally shot by humans or they can get caught in leg-hold traps. They can also collide with cars or other objects and get caught in barbed wire. Owls are sometimes poisoned by pesticides and other toxic substances that have accumulated in their prey.

Where do Great Horned Owls live?

Great Horned Owls live in a wide variety of habitats: deciduous, mixed, or conifer forests, but prefer open and secondary-growth temperate woodlands, swamps, orchards, and agricultural areas. Their home range usually includes some open habitat of fields, wetlands, pastures, or croplands.

Great Horned Owls are widespread. Populations occur to the north up to the tree line at the northern limits of taiga, 68°N. They occur in west and central Alaska, central Yukon Territory, northwest and southeast Northwest Territories, west central Manitoba, northern Ontario, northern Quebec and Anticosti Island, Fort Chimo in Ungava, Okak in Labrador, Prince Edward Island, and Newfoundland, south throughout Mexico and northern Central America, and locally throughout high latitudes of South America to Tierra del Fuego. They are absent from Kodiak Island in Alaska, Queen Charlotte Island in British Columbia, and the West Indies. They occur in appreciably lower densities in the Appalachian and Rocky Mountains. (e.g., rare in sub-alpine forest in Colorado), as well as in the Mojave and Sonoran deserts.

In Middle America, Great Horned Owls are resident throughout Mexico and south through the interior of north Central America to western Nicaragua, but they are absent from much of humid southeastern Mexico (except resident in central and northern Yucatán Peninsula); they are very rare in Costa Rica; there are only two records of Great Horned Owl for Panama. They do not occur in tropical mangroves on the northern coast of South America and are rare in Amazonia. They occur chiefly at 11,500 to 15,000 feet (3,500 to 4,500 meters) elevation through Venezuela and Colombia, and above 10,000 feet (3,000 meters) in the puna zone of Peru, western Bolivia, northwest Argentina, and northern Chile; they are common in Patagonia and Magallanes, Chile. They are also found as high as the treeless barranca zone of Ecuadorian Andes at more than 14,000 feet (4,300 meters).

Even northernmost populations are resident, with no sign of annual migration.

How many Great Horned Owls are there?

There are few population estimates available. Great Horned Owls are widespread, but thinly distributed. According to the North American Breeding Bird Survey, between 1966 and 2010 Great Horned Owl populations were stable in the U.S. but declined in Canada, resulting in an overall population decline just under 1 percent per year (resulting in a cumulative loss of 30 percent). Partners in Flight estimates the global breeding population at 6 million with about 45 percent of the population in the U.S., 14 percent in Canada, and 7 percent in Mexico. Great Horned Owls were heavily hunted until the practice was abolished in the mid-twentieth century. Some illegal hunting continues. Northern populations rise and fall in cycles along with prey populations. The species adapts well to habitat change as long as nest sites are available. In the Pacific Northwest they have expanded into open land recently created by logging. Because of their prowess as predators, Great Horned Owls can pose a threat to other species of concern, such as Peregrine Falcons and Spotted Owls. Owls are sometimes poisoned by pesticides and other toxic substances that have accumulated in their prey.

Do Great Horned Owls migrate? When will they migrate? Where will they go? Will they stay together when they migrate?

Great Horned Owls do not migrate annually; most individuals are permanent residents. Irruptions from Saskatchewan and Alberta are documented, showing striking southeasterly movements, but this is not really a true migration. These irruptions happen chiefly when there are population crashes of the snowshoe hare occurring in boreal forests and aspen parklands. Such individuals, including many adults, travel to Dakotas, Minnesota, Nebraska, Kansas, and Iowa—often part of the periodic invasion of Minnesota and Wisconsin by this species and the Northern Goshawk at roughly 10-year intervals. The longest known distance traveled by a Great Horned Owl is 1,279 miles (2,058 kilometers) from Alberta to western Illinois.

How long do Great Horned Owls live?

This species is probably the most long-lived of North American owls. The oldest Great Horned Owl on record was at least 28 years old when it was found in Ohio in 2005. Four Cincinnati-area Great Horned Owls survived for more than 20 years. All were recovered within 20 kilometers of their nests, including one that was taken to a rehabilitation center after being injured along a highway. The bird was 28 years old at the time and survived in captivity until age 34 years 10 months.

Are Great Horned Owls aggressive? How do they attack?

In both adults and older young, at least three forms of threat display are evident. Mild threats consist of agitated bill-clapping, hissing, occasional low, drawn-out screams, and other guttural noises. The second threat level consists of fully spread wings arching in a “wall” toward any intruder, while the owl’s head is held either beneath the wings, the bill almost touching the ground, or upright. This threat may also be accompanied by agitated bill-clapping, screams, and other guttural noises. The third threat level consists of spread wings, bill-clapping, hissing, higher-pitched screams of a longer duration, with the body poised to strike feet-first at an intruder. If the intruder does not back down, the owl will “hop” forward and strike it with feet, attempting to grasp and rake with its claws.

What can I do to help Great Horned Owls?

You can help Great Horned Owls by being a good steward to the environment. Choose environmentally friendly products when using cleaners and pesticides. Don’t lure owls into harm’s way by tossing food out near a road; this attracts rodents and raptors may swoop down to capture prey only to get hit by vehicles. Populations are robust and are not currently in need of management. However, artificial nest sites encourage breeding in areas with limited nest sites.

By reporting sightings of Great Horned Owls you can help scientists get a better understanding of their distribution and whether their numbers are stable, increasing, or decreasing. A real-time, online checklist program, eBird, has revolutionized the way that the birding community reports and accesses information about birds. eBird shares observations with a global community of educators, land managers, ornithologists, and conservation biologists. In time these data will become the foundation for a better understanding of bird distribution across the Western Hemisphere and beyond.

Cameras

When was the camera installed?

The camera was installed July 17—18, 2014, with funding from Skidaway Audubon and approval from The Landings Club Board of Governors. Southside Fire assisted in the installation by providing a ladder truck to reach above the nest, 80 feet high. Tim Sears from HDOnTap, Del Mar, California, arrived with the camera, enclosure, and custom mount. Tim also installed the Explore.org, Owl Research Institute, and Cornell Lab Snowy Owl cam in 2014 in Barrow, Alaska. The Cornell Lab’s Bird Cams Project Leader, Charles Eldermire, was also present during the installation.

Do the cameras bother the owls?

No, the owls usually ignore the cameras.

The camera was installed before the breeding season so as not to disturb nesting birds. The camera will not be visited for maintenance while birds are present in the nest or nearby. The only exception to this would be the need for emergency maintenance to protect the owls and the nest, e.g. if the camera falls on the nest due to broken tree limbs after high winds. The camera has been installed by an expert and is being overseen by a raptor expert. The camera is at a safe distance from the nest so that it does not interfere with owl activity, the safety of the owls, and the integrity of the nest site. If you are considering visiting the site we advise you to keep a safe distance from the nest to avoid disturbing the birds.

What type of cameras do you use?

Why is the nest so bright at night?

We are using a camera that can pick up infrared light. These types of cameras can see infrared light reflected off objects such as the nest, birds, and eggs. Neither the owls nor humans can see this part of the light spectrum with the naked eye.